Field of the Invention
The present invention relates an image processing apparatus, an optical apparatus, an image processing method, and a non-transitory computer-readable storage medium.
Description of the Related Art
Unsharp mask processing, in which differences between a blurred image and an input image are added to, or subtracted from, the input image to sharpen the input image, has been known. In Japanese Patent No. (“JP”) 4618355, a method to reduce an influence of a Point Spread Function (PSF) of an optical system by applying an asymmetrical one-dimensional filter to a pixel signal row in an image height direction is proposed.
In the conventional unsharp mask processing using a rotationally symmetrical filter as the unsharp mask, it is difficult to sharpen an image that was deteriorated by a PSF having a complicated shape such as an asymmetrical aberration and a sagittal halo. That is, when an attempt to correct an aberration in an azimuth direction in which a large quantity of aberration occurs is performed, undershoot is generated in an azimuth direction in which a small quantity of aberration occurs, and an attempt to restrain the undershoot cannot fully correct the aberration.
The method disclosed in JP 4618355 considers only the asymmetry in the image height direction that is an azimuth direction of a meridional surface and, as the filter is one-dimensional, cannot improve the asymmetry in a direction other than the image height direction. Moreover, as the asymmetry of the filter adjusted by the number of minus tap coefficients is different from the blur caused by the PSF of the optical system, sufficient sharpening of the image is unavailable.
Further, in the conventional unsharp mask processing using a rotationally symmetrical filter, controlling a correction intensity is performed, but control of balance for each frequency is unconsidered. Thus, when the correction is strengthened to advance an effect of sharpening, noise on a high frequency side particularly increases, and when the correction is weakened, the problem of the noise is resolved, but the effect of the sharpening decreases.